Aircraft provided with a buoyancy system, and a buoyancy method

1. An aircraft having a buoyancy system, the buoyancy system comprising: a plurality of floats, each float of the plurality of floats folded in flight other than during a stage of ditching, the buoyancy system including a deployment system for deploying each float of the plurality of floats outside an airframe of the aircraft, the plurality of floats comprising a plurality of main floats and a plurality of secondary floats, wherein the buoyancy system is configured to deploy the main floats outside the airframe in flight prior to ditching and to deploy the secondary floats outside the airframe after ditching, wherein the plurality of floats forms a plurality of float units, each float unit having a main float and a secondary float arranged side by side, a main float of a float unit arranged transversely between the secondary float of the float unit and the airframe, wherein the deployment system comprises at least one main inflator in fluid flow communication with only at least one main float to inflate only the at least one main float, the deployment system including at least one secondary inflator distinct from the at least one main inflator and in fluid flow communication with only at least one secondary float in order to inflate only the at least one secondary float.

2. The aircraft according to claim 1 , wherein the plurality of float units comprises at least one pair of float units, the at least one pair of float units comprising two float units arranged transversely on either side of the airframe.

3. The aircraft according to claim 2 , wherein the two float units of a pair of float units are arranged symmetrically on either side of the airframe.

4. The aircraft according to claim 1 , wherein each main float is connected to the airframe by at least one main cord.

5. The aircraft according to claim 1 , wherein each secondary float is connected to the airframe by at least one secondary cord.

6. The aircraft according to claim 1 , wherein a secondary float and a main float have a partition in common.

7. The aircraft according to claim 1 , wherein a secondary float is stitched and/or adhesively bonded to a main float.

8. The aircraft according to claim 1 , wherein each secondary float is in fluid flow communication with at least one main float via a valve, the deployment system comprising at least one main inflator in fluid flow communication with the main floats in order to inject a fluid into the main floats, and the main inflator in fluid communication with the secondary floats via the valve in order to inject the secondary float with fluid.

9. The aircraft according to claim 8 , wherein the valve is a passive valve, the passive valve opening when pressure existing in the main float provided with the passive valve exceeds a threshold, the pressure less than the threshold prior to ditching.

10. The aircraft according to claim 8 , wherein the aircraft includes a processor unit, the valve is an active valve, the active valve is connected to the processor unit, and the active valve is controlled by the processor unit.

11. A buoyancy system for an aircraft, the buoyancy system comprising: a plurality of floats comprising at least one pair of main floats and at least one pair of secondary floats, each float of the plurality of floats folded during a stage of flight; a deployment system for deploying each float of the plurality of floats outside an aircraft during at least one stage of ditching, the deployment system configured to: inflate the main floats during at least one of the stages of ditching prior to the aircraft reaching the liquid surface; and subsequent to inflating of the main floats, inflate the secondary floats after the main floats without deflating the main floats.

12. The buoyancy system of claim 11 , wherein the plurality of floats forms at least a pair of float units arranged transversely on either side of the aircraft, each float unit having a main float arranged transversely between the secondary float of the float unit and the aircraft.

13. The buoyancy system of 12 , wherein the deployment system is further configured to: inflate the main floats during a first stage of ditching while the aircraft is still in flight; and subsequently inflate the secondary floats during a second stage of ditching after the first stage of ditching.

14. The buoyancy system of claim 13 , wherein the deployment system comprises at least one main inflator in fluid flow communication with only the main floats to inflate only the main floats after the first stage of ditching, and at least one secondary inflator distinct from the at least one main inflator and in fluid flow communication with only at the secondary floats to inflate only the secondary floats after the second stage of ditching.

15. The buoyancy system of claim 13 , further comprising a valve disposed between the main floats and the secondary floats, wherein the valve is a passive valve opening when pressure existing in the main float exceeds a threshold, the pressure less than the threshold prior to ditching.

16. The buoyancy system of claim 13 , further comprising a valve disposed between the main floats and the secondary floats, wherein the deployment system comprises a processor unit and at least one inflator, the inflator in fluid flow communication with the main floats to inflate only the main floats during the first stage of ditching, and during the second stage of ditching, the processor controls the valve to inflate the secondary floats through the main floats.